The present invention relates to an apparatus and method for use in manufacturing a semiconductor device; and, more particularly, to an apparatus and method for use in forming films on surfaces of one or more substrates such as semiconductor substrate and glass substrate and improving the film quality.
In the semiconductor industry, various kinds of films are manufactured by thermal chemical vapor deposition (CVD) method. Some of them are acceptable without further treatment but others may need pre-deposition treatment and/or post-deposition treatment in order to achieve a desired performance.
An example of the latter case requiring a further treatment is tantalum pentoxide (Ta2O5) film which is used as a capacitor insulating film for semiconductor memory and the like. In a process for forming a tantalum oxide film as an insulating film for a capacitor portion of a 64 megabit-DRAM, volatized tantalum pentaethoxide (Ta(OC2H5)5) gas as a precursor and oxygen gas are delivered into a reaction chamber maintaining a predetermined temperature and reacted with a Si wafer, to thereby form an oxide film.
During the deposition process of the tantalum oxide film, carbon included in the precursor, i.e., tantalum pentaethoxide (Ta(OC2H5)5) may be introduced into tantalum pentoxide film and, when the amount of the carbon in the film exceeds a certain level, the insulating characteristics of the film become deteriorated, thereby elevating the leakage current.
By treating the wafer in a gaseous atmosphere including oxygen as a component thereof, carbon is removed from the film in the form of carbon dioxide and the concentration of the carbon in the film becomes decreased, thereby lowering the leakage current. Further, oxygen, which is generally insufficiently incorporated into the growing film during the deposition process, may also be supplied to the film.
One of the techniques for post-processing a tantalum oxide film is a furnace annealing method. In this method, thermal treatment is performed on a deposited tantalum pentoxide (Ta2O5) film at a temperature of higher than 800xc2x0 C. in an atmosphere of a gas including oxygen as a component thereof, e.g., O2, O3 (ozone), N2O or NO. Conventionally, the deposition process is performed at a temperature equal to or lower than 500xc2x0 C., which is considerably different from post-processing temperature, and, therefore, the post-deposition treatment is normally performed in a separate chamber or a separate apparatus.
In an alternative post-deposition treatment, the wafer is treated by active species generated from the plasma of gases including oxygen as a component thereof, e.g., O2, O3, N2O or NO.
Without such post-deposition treatments, the leakage current level may be so high that the tantalum pentoxide film cannot function properly as a capacitor insulating film.
FIG. 1 shows compositional depth profiles of the elements included in the tantalum oxide film manufactured by the above mentioned deposition process at a temperature of 470xc2x0 C. The abscissa of this graph represents the depth from the surface of tantalum oxide film and the ordinate at the left provides the atom concentrations (atoms/cc) of C, H and N, and the ordinate at the right shows the secondary ion counts (counts/sec) of Ta and Si. The thickness of the tantalum oxide film is 100 xc3x85.
As shown in FIG. 1, a very small amount of carbon is included at the interface between the Si wafer and the tantalum oxide film but this amount of carbon can be sufficient enough to deteriorate the film quality, i.e., entail a leakage current. In order to remove carbon from the interface to thereby reduce the amount of leakage, therefore, the substrate is processed by oxygen after the film forming. Specifically, oxygen annealing is performed at a temperature of higher than 800xc2x0 C. after the film forming.
FIG. 2 provides compositional depth profiles of a tantalum oxide film formed at 450xc2x0 C. and oxygen-annealed at 600xc2x0 C. in a reduced pressure. The abscissa of this graph shows the depth from the surface of the substrate and the ordinate at the left shows the atom concentrations (atoms/cc) of C, H and N, and the ordinate at the right shows the secondary ion counts (counts/sec) of Ta and Si. The thickness of the tantalum oxide film is 100 xc3x85.
It is apparent from FIG. 2 that the concentration of hydrogen is decreased but carbon still remains at the interface.
Meanwhile, in order to meet the requirement of low temperature process, it is preferable to perform the oxygen annealing by using plasma. The temperature of wafer can be lowered to 300-400xc2x0 C. during the process of using plasma. As an apparatus for plasma treatment, the so-called down-flow type apparatus appeared recently, in which the reactive gas flows downward from an upper region of the reaction chamber. This type of apparatus is preferable for achieving uniformity of film quality.
FIG. 3 shows a cross-sectional view of a down-flow type apparatus.
The apparatus includes an airtight reaction chamber 151 having walls 152 made of, e.g., stainless steel and a plasma chamber 154, arranged above the reaction chamber for generating plasma 153. The plasma chamber 154 has a quartz window 155 at its side and a coil 156 is arranged at the outer side of the quartz window 155. The coil 156 generates induced magnetic fields in the plasma chamber 154. A reactive gas inlet 157 is provided on top of the plasma chamber 154. In the reaction chamber 151, a substrate such as a wafer 158 is loaded on a wafer holder 159 having a built-in heater 160 for heating the wafer 158.
The apparatus is operated as follows.
The reaction chamber 151 and plasma chamber 154 are evacuated by an exhaust pump (not shown) through an exhaust port 161 and then a reactive gas of a predetermined flow rate is introduced through the reactive gas inlet 157 into the chambers 151, 154. After the inner pressure of the chambers 151, 154 becomes stabilized at a certain level, high frequency power is applied to the coil 156 from a high frequency power supply (not shown) in order to generate plasma 153 in the plasma chamber 154 and the substrate is processed by the plasma.
The plasma 153 generated in the plasma chamber 154 is spaced apart from the wafer 158 and only the neutral active species are provided to the wafer surface in the form of a down-flow 162.
Oxygen is generally used as the reactive gas. In the apparatus shown in FIG. 3, oxygen radicals (O*) activated by the plasma 153 is provided in the form of a down-flow 162 to the wafer surface to react with carbon and thereby remove carbon from the surface region of the wafer 158.
In this oxygen plasma treatment, the amount and the lifetime of the oxygen radicals may vary with the chamber pressure. Therefore, the flow rate of oxygen gas and the pressure of the plasma chamber 154 are controlled by, e.g., an exhaust pump. Typically, the process is performed under a chamber pressure of 1-100 Pa.
Such conventional type apparatus shown in FIG. 3 may have such deficiencies as: a) release of metal particles from the walls 152 of the reaction chamber 151 which is made of metal such as stainless steel; and b) high energy particles provided by the plasma 153.
The released metal contaminants may be incorporated into the wafer 158 or the film thereon to thereby reduce the yield.
The high energy particles from the plasma 153 may cause the metal contaminants released from the walls 152 of the reaction chamber 151 and also directly create physical and electrical defects in the wafer 158.
The apparatus shown in FIG. 3 is of a cold-wall type, in which only the wafer holder 159 is heated to a desired temperature.
This may entail other problems. Since the heat transfer to the wafer 158 may not be performed uniformly due to the bending and/or surface roughness of the wafer 158, it is difficult to heat the wafer 158 uniformly in a temperature range of 500xc2x0 C.xc2x11%. In order to solve this problem, electrostatic chuck has been contemplated. However, the use of a heater incorporated with an electrostatic chuck is not reliable in its wafer holding function and too costly to be used as a supply item.
Further, not all carbon contaminants in a relatively thick oxide film may be removed by a single post-deposition treatment: that is, post-deposition treatment may be effective only at a proximate portion of the film surface and may not affect the deeper portion of the film. As the semiconductor devices become more micro-structured and integrated, higher film quality, e.g., lower leakage level for tantalum pentoxide film, is required. This requirement may be fulfilled by repeating the deposition and post-deposition processes a multiple number of times, wherein the effect of post-deposition treatment may be uniformly achieved through the entire depth of film.
In the conventional type apparatus, a deposition process and a post-deposition process are performed in two separate chambers. Therefore, if these two processes are repeatedly performed in separate chambers, productivity becomes lowered due to, e.g., by the increased time for conveying the wafer between the chambers.
It is, therefore, an object of the present invention to provide an apparatus and a method for use in manufacturing a semiconductor device wherein a substrate to be processed is substantially not affected by the metal contaminants released from the chamber walls or the high energy particles emitted from the plasma and wherein the substrate can be uniformly heated to a relatively high temperature.
It is another object of the present invention to provide an apparatus and a method for use in manufacturing a semiconductor device capable of performing a deposition process and a pre- and/or a post-deposition process in an efficient manner.
In accordance with one aspect of the present invention, there is provided an apparatus for use in manufacturing a semiconductor device, comprising: a reaction chamber wherein one or more substrates to be treated are disposed; a plasma source arranged outside of and in proximity to the reaction chamber; an active species supply port for providing active species generated by the plasma source to the reaction chamber and arranged at a side of the reaction chamber; and, an exhaust port provided at the opposite side to the active species supply port, wherein the active species flows parallel to the surfaces of the substrates.
By arranging the plasma source outside of and in proximity of the reaction chamber, the substrates can be treated without metal contamination and damages by the plasma. Further, more than one substrate can be treated by supplying the active species flowing parallel to the substrates, thereby enhancing the throughput.
In accordance with a preferred embodiment of the invention, there is provided an apparatus for use in manufacturing a semiconductor device, comprising: means for supplying a film forming gas into a reaction chamber; and, a plasma source for generating active species supplied to one or more substrates to be treated.
By this constitution, the film forming process and the plasma treatment process can be performed in a same chamber.
As another aspect of the present invention, there is provided a method for use in manufacturing a semiconductor device by performing a predetermined treatment to one or more substrates, comprising the steps of: generating active species in a plasma source arranged outside of a reaction chamber; and, supplying active species flowing in a direction substantially parallel to the substrates.
In accordance with a preferred embodiment of the present invention, there is provided a method for use in manufacturing a semiconductor device, comprising the steps of: film forming on one or more substrates by thermal CVD method; and, plasma treating on the substrates.